diff --git a/2022/13.cpp b/2022/13.cpp
index 9386918..1ff6232 100644
--- a/2022/13.cpp
+++ b/2022/13.cpp
@@ -12,6 +12,7 @@
 
 #include <doctest.h>
 
+#include <aocpp/Parsing.hpp>
 #include <aocpp/Startup.hpp>
 
 namespace {
@@ -69,13 +70,12 @@ auto operator<(Packet const& lhs, Packet const& rhs) -> bool {
 // Packets can be integer literals or a list of packets.
 // A list of packets is bracketed with square brackets and is comma-separated.
 // No additional whitespace is tolerated in the input stream.
-template <typename It>
-class Grammar : public qi::grammar<It, PacketPairs()> {
-  qi::rule<It, std::int64_t> integer;
-  qi::rule<It, Packets()> packets;
-  qi::rule<It, Packet()> packet;
-  qi::rule<It, PacketPair()> packetPair;
-  qi::rule<It, PacketPairs()> packetPairs;
+class Grammar : public qi::grammar<std::string::const_iterator, PacketPairs()> {
+  qi::rule<iterator_type, std::int64_t> integer;
+  qi::rule<iterator_type, Packets()> packets;
+  qi::rule<iterator_type, Packet()> packet;
+  qi::rule<iterator_type, PacketPair()> packetPair;
+  qi::rule<iterator_type, PacketPairs()> packetPairs;
 
 public:
   Grammar() : Grammar::base_type{packetPairs} {
@@ -91,22 +91,6 @@ public:
   }
 };
 
-/// Parse the complete input stream according to the rules defined in 'Grammar'.
-/// Throws: std::runtime_error on failed parse
-auto Parse(std::istream & in) -> PacketPairs
-{
-  auto result = PacketPairs{};
-  auto const content = std::string{std::istreambuf_iterator{in}, {}};
-  auto b = content.begin(); // updated on successful parse
-  auto const e = content.end();
-
-  if (!qi::parse(b, e, Grammar<decltype(b)>{}, result) || b != e) {
-    throw std::runtime_error{"Bad packet: " + content};
-  }
-
-  return result;
-}
-
 // Return the sum 1-based indexes of the pairs where the first element is less than the second.
 auto Part1(PacketPairs const& packetPairs) -> std::size_t
 {
@@ -183,7 +167,7 @@ TEST_SUITE("2022-13 examples") {
       "[1,[2,[3,[4,[5,6,7]]]],8,9]\n"
       "[1,[2,[3,[4,[5,6,0]]]],8,9]\n"
     };
-    auto const packetPairs = Parse(in);
+    auto const packetPairs = aocpp::ParseGrammar(Grammar{}, in);
     CHECK(13 == Part1(packetPairs));
     CHECK(140 == Part2(packetPairs));
   }
@@ -191,7 +175,7 @@ TEST_SUITE("2022-13 examples") {
 
 auto Main(std::istream & in, std::ostream & out) -> void
 {
-  auto const packetPairs = Parse(in);
+  auto const packetPairs = aocpp::ParseGrammar(Grammar{}, in);
   out << "Part 1: " << Part1(packetPairs) << std::endl;
   out << "Part 2: " << Part2(packetPairs) << std::endl;
 }
diff --git a/2022/14.cpp b/2022/14.cpp
index c0e4d90..f25884c 100644
--- a/2022/14.cpp
+++ b/2022/14.cpp
@@ -15,6 +15,7 @@
 
 #include <doctest.h>
 
+#include <aocpp/Parsing.hpp>
 #include <aocpp/Startup.hpp>
 #include <aocpp/Coord.hpp>
 
@@ -28,11 +29,10 @@ using Input = std::vector<std::vector<aocpp::Coord>>;
 const aocpp::Coord TOP {500, 0};
 
 // Input file grammar
-template <typename It>
-class Grammar : public qi::grammar<It, Input()> {
-  qi::rule<It, aocpp::Coord> coord;
-  qi::rule<It, std::vector<aocpp::Coord>()> line;
-  qi::rule<It, Input()> input;
+class Grammar : public qi::grammar<std::string::const_iterator, Input()> {
+  qi::rule<iterator_type, aocpp::Coord> coord;
+  qi::rule<iterator_type, std::vector<aocpp::Coord>()> line;
+  qi::rule<iterator_type, Input()> input;
 
 public:
   Grammar() : Grammar::base_type{input} {
@@ -46,22 +46,6 @@ public:
   }
 };
 
-/// Parse the complete input stream according to the rules defined in 'Grammar'.
-/// Throws: std::runtime_error on failed parse
-auto Parse(std::istream & in) -> Input
-{
-  auto result = Input{};
-  auto const content = std::string{std::istreambuf_iterator{in}, {}};
-  auto b = content.begin(); // updated on successful parse
-  auto const e = content.end();
-
-  if (!qi::parse(b, e, Grammar<decltype(b)>{}, result) || b != e) {
-    throw std::runtime_error{"Bad input file: " + content};
-  }
-
-  return result;
-}
-
 auto ExpandLines(Input const& lines) -> std::unordered_set<aocpp::Coord>
 {
   auto result = std::unordered_set<aocpp::Coord>{};
@@ -175,7 +159,7 @@ TEST_SUITE("2022-14 examples") {
       "498,4 -> 498,6 -> 496,6\n"
       "503,4 -> 502,4 -> 502,9 -> 494,9\n"
     };
-    auto const input = Parse(in);
+    auto const input = aocpp::ParseGrammar(Grammar{}, in);
     auto const bottom = FindBottom(input);
     auto world = ExpandLines(input);
     CHECK(24 == Part1(bottom, world));
@@ -185,7 +169,7 @@ TEST_SUITE("2022-14 examples") {
 
 auto Main(std::istream & in, std::ostream & out) -> void
 {
-  auto const input = Parse(in);
+  auto const input = aocpp::ParseGrammar(Grammar{}, in);
   auto const bottom = FindBottom(input);
   auto world = ExpandLines(input);
   out << "Part 1: " << Part1(bottom, world) << std::endl;
diff --git a/2022/15.cpp b/2022/15.cpp
index 48b6fae..efb14e7 100644
--- a/2022/15.cpp
+++ b/2022/15.cpp
@@ -12,6 +12,7 @@
 #include <doctest.h>
 
 #include <aocpp/Coord.hpp>
+#include <aocpp/Parsing.hpp>
 #include <aocpp/Startup.hpp>
 
 namespace {
@@ -27,11 +28,10 @@ struct Entry {
 using Input = std::vector<Entry>;
 
 // Input file grammar
-template <typename It>
-class Grammar : public qi::grammar<It, Input()> {
-  qi::rule<It, aocpp::Coord> coord;
-  qi::rule<It, Entry()> entry;
-  qi::rule<It, Input()> input;
+class Grammar : public qi::grammar<std::string::const_iterator, Input()> {
+  qi::rule<iterator_type, aocpp::Coord> coord;
+  qi::rule<iterator_type, Entry()> entry;
+  qi::rule<iterator_type, Input()> input;
 
 public:
   Grammar() : Grammar::base_type{input} {
@@ -50,22 +50,6 @@ public:
   }
 };
 
-/// Parse the complete input stream according to the rules defined in 'Grammar'.
-/// Throws: std::runtime_error on failed parse
-auto Parse(std::istream & in) -> Input
-{
-  auto result = Input{};
-  auto const content = std::string{std::istreambuf_iterator{in}, {}};
-  auto b = content.begin(); // updated on successful parse
-  auto const e = content.end();
-
-  if (!qi::parse(b, e, Grammar<decltype(b)>{}, result) || b != e) {
-    throw std::runtime_error{"Bad input file: " + content};
-  }
-
-  return result;
-}
-
 struct Range {
   std::int64_t lo, hi;
   auto operator<=>(Range const& rhs) const = default;
@@ -235,7 +219,7 @@ TEST_SUITE("2022-15 examples") {
       "Sensor at x=14, y=3: closest beacon is at x=15, y=3\n"
       "Sensor at x=20, y=1: closest beacon is at x=15, y=3\n"
     };
-    auto const input = Parse(in);
+    auto const input = aocpp::ParseGrammar(Grammar{}, in);
     CHECK(26 == Part1(input, 10));
     CHECK(56000011 == Part2(input, 20));
   }
@@ -243,7 +227,7 @@ TEST_SUITE("2022-15 examples") {
 
 auto Main(std::istream & in, std::ostream & out) -> void
 {
-  auto const input = Parse(in);
+  auto const input = aocpp::ParseGrammar(Grammar{}, in);
   out << "Part 1: " << Part1(input, 2'000'000) << std::endl;
   out << "Part 2: " << Part2(input, 4'000'000) << std::endl;
 }
diff --git a/2022/16.cpp b/2022/16.cpp
index fb80757..e308034 100644
--- a/2022/16.cpp
+++ b/2022/16.cpp
@@ -28,6 +28,7 @@
 
 #include <doctest.h>
 
+#include <aocpp/Parsing.hpp>
 #include <aocpp/Startup.hpp>
 
 namespace {
@@ -80,25 +81,16 @@ struct Room {
   std::vector<std::string> connections;
 };
 
-/// @brief Parse the input file
-/// @param[in,out] in input stream
-/// @return Vector of parsed rooms, one per input line
-///
-/// The parser will consume input until the end of the stream.
-///
-/// Input lines should follow the following pattern:
-/// * Valve **name** has flow rate= **number** ; tunnels lead to valves **name**, **name** ...
-/// * Valve **name** has flow rate= **number** ; tunnel leads to valve **name**
-auto Parse(std::istream & in) -> std::vector<Room>
-{
-  auto result = std::vector<Room>{};
-  auto line = std::string{};
-  while (std::getline(in, line)) {
-    using namespace qi::labels;
-    using It = std::string::const_iterator;
+class Grammar : public qi::grammar<std::string::const_iterator, std::vector<Room>()> {
+  qi::rule<iterator_type, std::string()> name;
+  qi::rule<iterator_type, Room()> room_description;
+  qi::rule<iterator_type, std::vector<Room>()> room_descriptions;
 
-    qi::rule<It, std::string()> const name = qi::as_string[+qi::alpha];
-    qi::rule<It, Room()> const room_description =
+public:
+  Grammar() : grammar::base_type{room_descriptions} {
+    using namespace qi::labels;
+    name = qi::as_string[+qi::alpha];
+    room_description =
       "Valve " >>
       name [ phx::bind(&Room::name, _val) = _1 ] >>
       " has flow rate=" >>
@@ -107,18 +99,11 @@ auto Parse(std::istream & in) -> std::vector<Room>
       " lead"     >> -qi::string("s") >>
       " to valve" >> -qi::string("s") >>
       " " >>
-      (name % ", ") [ phx::bind(&Room::connections, _val) = _1 ];
-
-    auto b = line.cbegin();
-    auto const e = line.cend();
-    result.emplace_back();
-    if (!qi::parse(b, e, room_description, result.back()) || b != e) {
-      throw std::runtime_error{"bad input line"};
-    }
+      (name % ", ") [ phx::bind(&Room::connections, _val) = _1 ] >>
+      "\n";
+    room_descriptions = *room_description;
   }
-
-  return result;
-}
+};
 
 /// @brief Rearrange the rooms so that those with flows come first
 /// @param[in,out] rooms vector of rooms that gets reordered
@@ -287,7 +272,7 @@ auto Part2(
 /// @param[in,out] out output text
 auto Main(std::istream & in, std::ostream & out) -> void
 {
-  auto rooms = Parse(in);
+  auto rooms = aocpp::ParseGrammar(Grammar{}, in);
   auto const n = FlowsFirst(rooms); // reorders rooms
   auto const [start, distances] = GenerateDistances(rooms);
   rooms.resize(n); // forget about the rooms with no flow
diff --git a/2022/21.cpp b/2022/21.cpp
index babe1e2..b8f7181 100644
--- a/2022/21.cpp
+++ b/2022/21.cpp
@@ -15,6 +15,7 @@
 #include <z3++.h>
 
 #include <aocpp/Overloaded.hpp>
+#include <aocpp/Parsing.hpp>
 #include <aocpp/Startup.hpp>
 
 namespace {
@@ -38,14 +39,13 @@ struct Entry {
 using Input = std::vector<Entry>;
 
 // Input file grammar
-template <typename It>
-class Grammar : public qi::grammar<It, Input()> {
-  qi::rule<It, std::string()> variable;
-  qi::rule<It, Op()> op;
-  qi::rule<It, Expr()> expr;
-  qi::rule<It, std::variant<std::int64_t, Expr>()> rhs;
-  qi::rule<It, Entry()> line;
-  qi::rule<It, Input()> input;
+class Grammar : public qi::grammar<std::string::const_iterator, Input()> {
+  qi::rule<iterator_type, std::string()> variable;
+  qi::rule<iterator_type, Op()> op;
+  qi::rule<iterator_type, Expr()> expr;
+  qi::rule<iterator_type, std::variant<std::int64_t, Expr>()> rhs;
+  qi::rule<iterator_type, Entry()> line;
+  qi::rule<iterator_type, Input()> input;
 
 public:
   Grammar() : Grammar::base_type{input} {
@@ -69,22 +69,6 @@ public:
   }
 };
 
-/// Parse the complete input stream according to the rules defined in 'Grammar'.
-/// Throws: std::runtime_error on failed parse
-auto Parse(std::istream & in) -> Input
-{
-  auto result = Input{};
-  auto const content = std::string{std::istreambuf_iterator{in}, {}};
-  auto b = content.begin(); // updated on successful parse
-  auto const e = content.end();
-
-  if (!qi::parse(b, e, Grammar<decltype(b)>{}, result) || b != e) {
-    throw std::runtime_error{"Bad input file: " + content};
-  }
-
-  return result;
-}
-
 auto Eval(
   std::unordered_map<std::string, double> & values,
   std::unordered_map<std::string, Expr> const& exprs,
@@ -191,15 +175,15 @@ TEST_SUITE("2022-21 examples") {
       "drzm: hmdt - zczc\n"
       "hmdt: 32\n"
     };
-    auto const input = Parse(in);
+    auto const input = aocpp::ParseGrammar(Grammar(), in);
     CHECK(152 == Part1(input));
     CHECK(301 == Part2(input));
   }
 }
 
 auto Main(std::istream & in, std::ostream & out) -> void
-{
-  auto const input = Parse(in);
+{  
+  auto const input = aocpp::ParseGrammar(Grammar(), in);
   out << "Part 1: " << Part1(input) << std::endl;
   out << "Part 2: " << Part2(input) << std::endl;
 }
diff --git a/2022/24.cpp b/2022/24.cpp
new file mode 100644
index 0000000..2038297
--- /dev/null
+++ b/2022/24.cpp
@@ -0,0 +1,66 @@
+#include <cstdint>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include <boost/range/adaptor/indexed.hpp>
+
+#include <doctest.h>
+
+#include <aocpp/Coord.hpp>
+#include <aocpp/Startup.hpp>
+
+namespace {
+
+struct World {
+  std::vector<aocpp::Coord> ups, downs, lefts, rights;
+  std::size_t height, width;
+};
+
+auto Parse(std::istream & in) -> World
+{
+  auto result = World{};
+  auto y = std::size_t{0};
+  auto line = std::string{};
+
+  while (std::getline(in, line)) {
+    for (auto const [x,c] : boost::adaptors::index(line)) {
+      switch (c) {
+        case '>': result.rights.emplace_back(x-1,y-1); break;
+        case '<': result.lefts.emplace_back(x-1,y-1); break;
+        case '^': result.ups.emplace_back(x-1,y-1); break;
+        case 'v': result.downs.emplace_back(x-1,y-1); break;
+      }
+    }
+    ++y;
+  }
+
+  result.height = y - 2;
+  result.width = line.size() - 2;
+
+  return result;
+}
+
+} // namespace
+
+TEST_SUITE("2022-24 examples") {
+  TEST_CASE("example") {
+    std::istringstream in {
+      "#.#####\n"
+      "#.....#\n"
+      "#>....#\n"
+      "#.....#\n"
+      "#...v.#\n"
+      "#.....#\n"
+      "#####.#\n"
+    };
+    auto const world = Parse(in);
+  }
+}
+
+auto Main(std::istream & in, std::ostream & out) -> void
+{
+  auto const input = Parse(in);
+  //out << "Part 1: " << Part1(in) << std::endl;
+}
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 0ca5734..f21d974 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -1,2 +1,3 @@
 add_library(aocpp src/Startup.cpp src/Coord.cpp src/Parsing.cpp)
-target_include_directories(aocpp PUBLIC include)
\ No newline at end of file
+target_include_directories(aocpp PUBLIC include)
+target_link_libraries(aocpp Boost::headers)
\ No newline at end of file
diff --git a/lib/include/aocpp/Parsing.hpp b/lib/include/aocpp/Parsing.hpp
index 02b89ec..80d3188 100644
--- a/lib/include/aocpp/Parsing.hpp
+++ b/lib/include/aocpp/Parsing.hpp
@@ -2,12 +2,34 @@
 #define AOCPP_PARSING_HPP_
 
 #include <string>
+#include <iostream>
+#include <iterator>
 #include <vector>
 
+#include <boost/spirit/home/qi.hpp>
+
 namespace aocpp {
 
 auto SplitOn(std::string const& stuff, std::string const& sep) -> std::vector<std::string>;
 
+/// Parse the complete input stream according to the rules defined in 'Grammar'.
+/// Throws: std::runtime_error on failed parse
+template <typename G>
+auto ParseGrammar(G const& grammar, std::istream & in) -> typename G::start_type::attr_type
+{
+  namespace qi = boost::spirit::qi;
+  auto result = typename G::start_type::attr_type {};
+  auto const content = std::string{std::istreambuf_iterator{in}, {}};
+  auto b = content.begin(); // updated on successful parse
+  auto const e = content.end();
+
+  if (!qi::parse(b, e, grammar, result) || b != e) {
+    throw std::runtime_error{"Bad input file: " + content};
+  }
+
+  return result;
+}
+
 }
 
 #endif
\ No newline at end of file